Unbridged bicyclic cyclopentadienyl zirconocene complexes: Their possible application as fluxional catalysts in propene polymerization

Polo, Eleonora; Losio, Simona; Forlini, Fabrizio; Locatelli, Paolo; Provasoli, Augusto

doi:10.1002/1521-3935(200208)203:12<1859::aid-macp1859>3.0.co;2-0

Cited by 8 publications

(20 citation statements)

References 3 publications

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“…By taking advantage of a new synthetic pathway,6 that has proven successful for a versatile and “tuned” synthesis of tetrahydroindenyl systems and of related ligands, and on the basis of the results obtained with several zirconium complexes,7 we have focused our interest on bis[ η 5 ‐(2‐phenyl‐4,5,6,7,8‐hexahydroazulenyl)]titanium dichloride, C 7 Ph‐Ti ,8 whose corresponding zirconium derivative gave the best performance as a fluxional catalyst in propylene polymerization. We have also synthesized (IndPh) 2 TiCl 2 ( w‐Ti ) and taken it as a reference point, and ethylenebis[ η 5 ‐(2‐phenyl‐4,5,6,7,8‐hexahydroazulenyl)]titanium dichloride, EBC 7 Ph‐Ti , as a 1:1 rac/meso ‐mixture.…”

Section: Introductionmentioning

confidence: 99%

“…We have also synthesized (IndPh) 2 TiCl 2 ( w‐Ti ) and taken it as a reference point, and ethylenebis[ η 5 ‐(2‐phenyl‐4,5,6,7,8‐hexahydroazulenyl)]titanium dichloride, EBC 7 Ph‐Ti , as a 1:1 rac/meso ‐mixture. The results obtained with the new catalysts were compared with those provided by the corresponding zirconium complexes ( C 7 Ph‐Zr and w‐Zr )7,9 under the same polymerization conditions.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Refoldability and Thermoactivity of Fluorinated Phosphotriesterase

Baker

Montclare

2011

ChemBioChem

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced Refoldability and Thermoactivity of Fluorinated Phosphotriesterase

Baker

Montclare

2011

ChemBioChem

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“…Our aim was to investigate the possibility to observe a “fluxional behavior” and to obtain elPP, even in the absence of the aromatic ring, by introducing the conformational flexibility of the saturated ring as a new parameter. We studied several sets of complexes, concentrating our attention not only on the substituents on the indenyl ligand, but also on the role played by the saturated ring condensed to the cyclopentadienyl moiety . Up to then, the lack of a synthetic strategy able to allow systematic variations with respect to the basic catalyst structure, had prevented investigations of this kind.…”

Section: Introductionmentioning

confidence: 99%

Unbridged Zirconium and Titanium Metallocenes with Seven- or Eight-Saturated Fused-Ring Ligands: a Route for the Synthesis of Stereoblock Polypropene

Losio¹,

Zecchi²,

Bertini³

et al. 2005

Macromolecules

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Unbridged zirconocene catalysts, where a seven-or eight-membered ring fused to a cyclopentadiene is associated with a phenyl substituent in position 2 (C 7Ph-Zr and C8Ph-Zr), were tested, under the same polymerization conditions, to produce polypropenes with microstructure, molecular properties, and thermal behavior similar to those prepared with (IndPh)2ZrCl2 (w-Zr), the "classical" Waymouth catalyst. Different results were obtained from the homologue titanium catalysts (C7Ph-Ti and C8Ph-Ti) and from the titanium benzyl derivative (C7Bn-Ti), which produced quite heterogeneous materials with broad molecular weight and that can be separated into fractions spanning from completely atactic to fractions characterized by the presence of long isotactic blocks. A quite interesting behavior is observed with the zirconium benzyl derivative C7Bn-Zr, which produces good yields of a polymer with narrow polydispersity, which, despite its rather high isotacticity, shows a hardly detectable melting peak and is completely ether soluble. Quite surprisingly, the same sample, after prolonged annealing, shows a narrow melting peak at low temperature (55-65 °C). This result, together with the X-ray analysis, is in favor of a quite homogeneous material, capable of giving crystallites of small size.

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“…By taking advantage of a new synthetic pathway, [6] that has proven successful for a versatile and ''tuned'' synthesis of tetrahydroindenyl systems and of related ligands, and on the basis of the results obtained with several zirconium complexes, [7] we have focused our interest on bis [Z 5 -(2-phenyl-4,5,6,7,8-hexahydroazulenyl)]titanium dichloride, C 7 Ph-Ti, [8] whose corresponding zirconium derivative gave the best performance as a fluxional catalyst in propylene polymerization. We have also synthesized (IndPh) 2 -TiCl 2 (w-Ti) and taken it as a reference point, and ethylenebis [Z 5 -(2-phenyl-4,5,6,7,8-hexahydroazulenyl)]titanium dichloride, EBC 7 Ph-Ti, as a 1:1 rac/meso-mixture.…”

Section: Introductionmentioning

confidence: 99%

“…We have also synthesized (IndPh) 2 -TiCl 2 (w-Ti) and taken it as a reference point, and ethylenebis [Z 5 -(2-phenyl-4,5,6,7,8-hexahydroazulenyl)]titanium dichloride, EBC 7 Ph-Ti, as a 1:1 rac/meso-mixture. The results obtained with the new catalysts were compared with those provided by the corresponding zirconium complexes (C 7 Ph-Zr and w-Zr) [7,9] under the same polymerization conditions.…”

Section: Introductionmentioning

confidence: 99%

Effect of Titanium on Fluxional Behavior of Unbridged Metallocene Catalysts

Polo

Losio

Zecchi

et al. 2004

Macromol. Rapid Commun.

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Summary: Thanks to the use of a ligand consisting of a saturated ring fused to the cyclopentadienyl moiety, which sensibly increases the stability of titanocenes, it was possible to investigate the oscillating behavior of titanium catalysts in propylene polymerization for the first time. The titanium‐based catalysts yield poly(propylene)s with new and interesting microstructures. Indeed, in spite of the significantly lower isotactic pentad content [mmmm], the average lengths of the isotactic blocks (Niso) are similar or even higher than that obtained with the zirconium‐based homologues. Accordingly, differential scanning calorimetry (DSC) analysis shows melting peaks which are more evident than those obtained with the zirconium homologues. The study of the microstructure of the poly(propylene)s obtained with these catalysts allowed us to participate in the still open discussion on the oscillating mechanism of unbridged metallocenes.The titanium‐based catalysts employed in this study.imageThe titanium‐based catalysts employed in this study.

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Unbridged bicyclic cyclopentadienyl zirconocene complexes: Their possible application as fluxional catalysts in propene polymerization

Cited by 8 publications

References 3 publications

Enhanced Refoldability and Thermoactivity of Fluorinated Phosphotriesterase

Enhanced Refoldability and Thermoactivity of Fluorinated Phosphotriesterase

Unbridged Zirconium and Titanium Metallocenes with Seven- or Eight-Saturated Fused-Ring Ligands: a Route for the Synthesis of Stereoblock Polypropene

Effect of Titanium on Fluxional Behavior of Unbridged Metallocene Catalysts

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